Heavy Smoking as Teenager Might Add Pounds Later

THURSDAY Jan. 22, 2009 -- A surprising Finnish study casts doubts on the common assumption smokers have that their unhealthy habit helps keep them thin.

Specifically, the researchers found that teens who smoke heavily were more likely to grow up to be fat.

There's still no evidence that cigarettes directly cause obesity, but "this is one more thing people should take into account when they consider their smoking habits," said study author Dr. Suoma Saarni, a researcher at the University of Helsinki.

American experts, however, are somewhat skeptical of the findings, which are published in the February issue of the American Journal of Public Health.

Smoking has long been linked to thinness, not obesity. As Saarni pointed out, people who stop smoking often gain weight. And studies have suggested that some teens and adult women use smoking as a weight-loss tool.

In the new study, Saarni and colleagues looked at the findings from questionnaires given to 4,296 Finnish twins born between 1975 and 1979. They were studied at four points between the ages of 16 and 27.

The researchers found that those who smoked at least 10 cigarettes a day at ages 16 to 18 were more likely to be fat around the middle. The higher rate remained even when researchers adjusted their figures to account for the possible effects of other factors.

Women, meanwhile, were more likely to be obese.

The study didn't report how many more times the smokers were likely to be overweight or fat around the abdomen.

However, about 35 percent of the women who'd been heavy smokers were fat around the middle, compared to about 22 percent of those who never smoked. The difference was smaller in men.

Saarni cautioned that the study is the first to suggest such an association, and more research will need to be done to confirm the results. Still, people should take them into account, Saarni said.

Why might smoking lead to obesity? Saarni said it could have something to do with changes in the body's metabolism -- its ability to process food and keep fat from building up.

Michael Siegel, professor at Boston University School of Public Health, said there may not be a direct link.

Most likely, he said, "smokers tend to have a constellation of poor health habits, including poorer diet and less physical activity. It is most likely that these factors, and not the smoking itself, is causing them to become obese."

Dr. Ted Schettler, science director at the Science and Environmental Health Network, said the study is limited. Among other things, he said, it didn't examine the full diets of the twins to see if they ate more fatty foods.

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